Can you nest where you roost? Waterbirds use different sites but similar cues to locate roosting and breeding sites in a small Indian city

Abstract

Tropical cities provide challenging conditions for resident wild species to undertake critical activities such as roosting and breeding. Tree-nesting waterbirds are widespread urban inhabitants but how they choose sites for these critical activities in urban areas, and whether requirements vary by species, are poorly understood. We assessed whether waterbirds chose roosting and nesting sites using similar cues in a rapidly urbanising small Indian city, Udaipur. Roost sites (N = 78, 17 species especially Ardeola grayii, Bubulcus ibis, Pseudibis papillosa) were located mostly beside roads and wetlands. Nest sites (N = 130, 12 species especially B. ibis, P. papillosa and Anastomus oscitans) were different from roost sites and were located mostly in built-up areas and wetlands. Waterbirds used 23 of 39 available tree species for roosting and nesting, strongly preferring snags and the largest trees of introduced (Azadirachta indica), native (Ficus spp., Vachellia nilotica) and exotic (Eucalyptus sp.) species. Site locations for both activities were associated negatively with built-up areas at the smallest spatial scale. At larger spatial scales they were associated positively with wetlands and built-up areas, with waterbirds entirely avoiding the Aravalli mountains. Individual waterbird species displayed idiosyncrasies in choice of tree species but used similar cues to locate roost and nest sites. Retaining large trees and wetlands across Udaipur city is essential to allow space for waterbirds’ critical activities. The scale and diversity of waterbirds roosting and nesting in Udaipur city is unprecedented suggesting that the ability of small tropical cities to aid urban biodiversity conservation has been overlooked.